The broad objective of the proposed research is to determine the natural history of lysosomal enzymes in normal cells from patients with genetic diseases. This research is designed to deduce the mechanisms by which cells selectively internalize hydrolytic enzymes and package them into lysosomes. The cell surface receptors for lysosomal hydrolases will be purified and characterized. Anti-receptor antibodies will be raised and used to follow the endocytosis of receptor and define the mechanisms of receptor recycling. Lysosomal organelles, residual bodies and GERL, will be isolated from cultured human fibroblasts. Lysosomal membrane will be analyzed for lipid and protein content and compared to membranes of cells from patients with lysosomal abnormalities. Lysosome fusion will be examined in vitro to detect membrane and enzyme exchange. Model systems will be developed with purified lysosomes and artificial vesicles called liposomes, to establish the chemical requirements that control organelle fusion.